Regenerative turbine pump have double row vanes cut in the rim. The impeller rotates within two liners into which annular channels have been milled. Liquid flows in at the suction and is picked up by the impeller vanes. In completing nearly one revolution in the annular channel, the fluid develops a high velocity and pressure increases dramatically before being sent out the discharge. The liquid re-circulates between the impeller vanes and the annular chamber. Because of this action, the fluid flows in a path like a helical spring laid into each of the annular grooves as the fluid is carried forward. Energy is added to the fluid by a number of vortex impulses in the impeller vanes, as it travels from suction to discharge.
These impulses have the same effect as multi- staging in a centrifugal pump. In a multistage centrifugal pump, the pressure is the result of energy added in each stage. In a turbine pump, pressure is added to the fluid stream by circulating many times through the vanes of a single impeller.
One of the most remarkable features of the regenerative turbine pump is its performance characteristics when pumping highly volatile liquids. The manner in which the turbine impeller imparts velocity/energy to the fluid, as described above, is quite different from conventional centrifugal or positive displacement designs. The continuous, progressive building of pressure in a regenerative turbine pump essentially eliminates the sudden collapse of bubbles that is destructive cavitation.
A turbine pump can develop about ten times the discharge pressure of a centrifugal type having equal impeller diameter and speed. Pressure increases nearly uniformly around the impeller rim. At the impeller hub, the pressure is about one half the discharge pressure. This lower pressure, plus suction pressure, is what is seen in the stuffing box. Holes through the impeller keep the impeller centered to reduce wear, prevent unbalanced pressures on the impeller and reduce end thrust on the bearings.
REGENERATIVE PUMP DESIGN ADVANTAGES
- Develop higher pressures
- Can be run at lower motor speeds
- Eliminate cavitation
- Operate with lower NPSHr
- Deliver specified capacity with input pressure variations
- Meet performance with fewer stages
- Smaller size